1. Field of the Invention
This invention relates to magnetic components for use in sensors, transformers, electrical chokes, magnetic inductors and the like; and more particularly to a magnetic implement that exhibits linear magnetization in response to an applied magnetic field.
2. Description of the Prior Art
When a magnetic material is magnetized by an external magnetic field, “H”, a magnetic polarization or induction takes place in the material. The amount of the induction is measured as magnetic flux density, commonly termed “B”. A linear B-H characteristic is generally obtained for a soft magnetic material in which the magnetically easy axis lies perpendicular to the direction of the magnetic excitation. In such material, the external magnetic field H tends to tilt the average direction of the magnetic flux B so that the measured quantity B is proportional to H. Since the ideal linear B-H response is not easily achieved, most magnetic materials display non-linear B-H behavior. Any deviation from an ideal B-H linearity introduces corresponding deviations in the magnetic response to the externally applied field H.
A classical example of magnetic materials showing linear B-H characteristics is a cold-rolled 50% Fe—Ni alloy, called Isoperm. Among amorphous magnetic alloys, heat-treated Co-rich alloys have been known to provide linear B-H characteristics and are presently used as the magnetic core materials in current transformers. The Co-rich amorphous alloys in general have saturation inductions lower than about 10 kG, or 1 Tesla, which limits the maximum field levels that can be applied. A recent development has led to an Fe-based amorphous alloy that shows a linear B-H behavior when properly heat-treated. Such an Fe-based amorphous alloy and its heat treatment are disclosed by U.S. Pat. No. 6,749,695. This Fe-based material exhibits a saturation induction exceeding 10 kG or 1 Tesla, thereby extending the use of the linear B-H behavior into a higher magnetic excitation region.
Further extension of the B-H linear behavior to an even higher magnetic field is necessary to address the needs of magnetic devices operated in larger applied fields. These needs arise from the ever-increasing level of electrical current, which must be controlled or monitored in electrical power devices and power electronics. In the case of sensors, a high field capability would extend the upper current limit of existing devices. Magnetic materials that possess linear B-H behaviors are clearly needed by devices exposed to wider magnetic field excitation.